This is a fantastic plugin!
Two factor is available with email and others as well. Two factor SMS is not available, in part because SMS requires a third party subscription service to somewhere -- i.e., this is not free.
A couple of notes to keep in mind:
* By default, new users are "2FA Disabled". What this means is that you'll have to go back through each user and enable 2FA individually.
* 2FA can be manually disabled by each user. For example, if an Editor decides to turn off his 2FA, he can, even without Admin access. This can become a compliance issue.
* There is no "audit" for 2FA. This means that if a user is 2FA disabled, the Admins will not know it unless they manually search through the user list.
* There is no "User Bulk Action" to enable 2FA. This means that each user has to be individually 2FA Enabled.
* There is no integration with MainWP. This means you'll have to manage each of your sites individually -- manually logging into each site, going to the Users area, enabling 2FA individually for each user, when confirming 2FA enabled you'll have to go to each site individually as well.
It can be a lot of work when you are managing multiple sites
That all said, this is a FREE 2FA for all users and all sites. I give it absolutely a 5 Stars considering the other options that exist, none of which are free.
Thank you to the developers!

Just happened to upgrade server software with latest updates and it changed the time-zone to something different than I live in. Made Two Factor not work.
After I realized it and changed to proper time-zone, it worked perfectly.
Best 2 Factor plugin out there.